Known single nucleotide substitutions (point mutations) cause of a significant number of inherited diseases, e.g., sickle cell anemia, α- and β-thalassemia, phenylketonuria, hemophilia, α1-antitrypsin deficiency. Unknown point mutations may cause Huntington's chorea and cystic fibrosis (Antonarakis et al., (1985); Cooper and Schmidtke, (1986(a)(b)). No corrective measure at the molecular level is known. However, early diagnosis can often facilitate dietary and therapeutic interventions which may lead to an ameliorated clinical course of the disease. The continued development of more sensitive and precise diagnostic techniques, particularly those that enable detection of genetic diseases at the preclinical or prenatal stage, is therefore important.
Allele specific synthetic oligonucleotide (ASO) probes are widely used to detect target DNA sequences (Wallace, et al., (1979, 1981(a)(b); Conner et al., (1983)). Oligonucleotide competition techniques and stringent washing further enhance ASO probe selectivity (Nozari, et al., (1986); Wu, et al. (1989(a)).
PCR amplification and ASO hybridization have been combined to detect several DNA sequence polymorphisms, including those that cause certain genetic diseases (Saiki, R. K., et al., (1986, 1988(b); Impraim, et al., (1987); Chehab, et al., (1987); Farr, et al., (1988)).